1. Field of the Invention
The present invention relates, generally, to object proximity detection methods and apparatus. More particularly, the invention relates to object proximity detection methods using an optical sensor system that transmits and receives light radiation or optical signals. The optical signal may be steady-state, pulsed, digitally encoded, or a sequenced combination of the foregoing. The invention provides a means to control a variety of devices or processes based upon the presence or absence of an object or substance within some predetermined distance from and/or orientation to a fixed sensor. An object or substance is detected by transmitting digital data bursts of light radiation from a remote optical energy transmitter and verifying the error-free return of the digital data bursts into an optical energy receiver. The verification of the error-free return of the transmitted data bursts provides proof that, depending on the design of the sensor system, an object is either present and has reflected the optical energy into the receiver or is absent and has not blocked the optical energy from being received into the receiver. Additionally, the sensor system may be designed to detect characteristics of the detected object, such as the size, shape, and orientation of the object and/or the amount or portion of a substance contained by the object.
The apparatus and methods of this invention have particular utility used in conjunction with commercial and institutional food service beverage and ice dispensing systems, medical/pharmaceutical dispensing systems, automated manufacturing and production systems, food processing systems, packaging systems, and a variety of other commercial, industrial, municipal and residential systems that utilize one or more mechanical, electronic, optical, or similar sensors in their operations. For example, the apparatus and methods of this invention may be incorporated into a dispensing system to detect a container or target receptacle and to control the amount or portion of the product or substance dispensed into the container.
2. Background Information
The primary difficulty with using optical signals for object detection is distinguishing valid signals from ambient light energy noise. This invention employs digital data error detection principles to insure that the received signal accurately indicates the presence or absence of an object.
Noise rejection or avoidance in optical sensor systems has usually been attacked using one of two methods. The first method simply looks for "clean" time slots without noise and transmits signals during these clean time slots. The second method transmits a master-clocked continuous pulsed signal and a corresponding master-clocked synchronous signal, and verifies that the received signal exactly matches both the transmitted pulsed and synchronous signals. Methods for rejecting or avoiding noise in optical sensor systems are generally disclosed in the following U.S. patents: Skell et al., U.S. Pat. No. 5,744,793; Skell et al., U.S. Pat. No. 5,550,369; Skell et al., U.S. Pat. No. 5,491,333; Grozinger et al., U.S. Pat. No. 5,250,801; Schiller, U.S. Pat. No. 5,245,177; Kim, U.S. Pat. No. 4,973,834; Hatten et al., U.S. Pat. No. 4,282,430; Hosel, U.S. Pat. No. 5,002,102; Fukuyama et al., U.S. Pat. No. 4,306,147; Devale, U.S. Pat. No. 4,437,499; and Upton, U.S. Pat. No. 4,202,387.
Known portion control apparatus and methods for dispensing systems are shown in the following U.S. patents: Upton, U.S. Pat. No. 4,202,387 and Skell et al., U.S. Pat No. 5,744,793. Upton uses a set of photosensors to detect the presence and size of a container. Portion control is accomplished by controlling the pouring duration using timer circuitry according to the detected container size. Skell et al. ('793) accomplish portion control by monitoring the product level and disabling the dispenser once the dispensed product reaches a given height in the container. Two sets of transmitters and receivers are used. One set is positioned and oriented to detect the presence of the container. The transmitter of the other set is positioned and oriented to direct a signal toward an inside wall of a cup-like container. The receiver of the other set detects the reflected signal until the dispensed product reaches a predetermined level in the container and interferes with the signal. The dispenser continues to dispense product if the received signal matches the synchronous signal, and discontinues to dispense the product if the received signal does not match the synchronous signal.
This invention differs significantly from known art. No attempt is made to pre-filter the noise to a relatively low level with respect to the signal nor to identify "clean" time slots in which to transmit a signal. Moreover, this method does not depend on a master clock, a continuous pulsed signal, or a corresponding synchronous circuit. Rather, the present invention transmits a burst of digitally encoded data as required to control the equipment, system, or process that is the object of the design. Furthermore, both the data content and period between bursts are varied. This asynchronous transmission of digitally encoded data provides an effective method for distinguishing valid signals from ambient light energy noise.